In order to minimize UE (user equipment) state transitions between a connection state and an idle state, it is needed to define one or more methods to keep the UE in a connection state while reducing signaling overheads in the connection state through for example modifying the value of the parameters for measurement reporting and handover behavior, and reducing power consumption through for example adjusting DRX (Discontinuous Reception) cycle.
In order to achieve the above method(s), the eNB (evolved Node B) may employ user inactivity timer to a very longer value. The purpose is to reduce the signaling overhead of frequent RRC (Radio Resource Control) connection establishments. The main benefits of the method are: it doesn't have specification change to the protocol, and greatly reduces the signaling overhead.
However, this method has many problems:
First, keeping the UE in the connection state will consume considerable amount of UE power because UE will send small amounts of data often, for example, maintenance of UE timing advance, periodic channel sounding, and measurement reports.
Second, whether the control channel is sufficient to support a large number of UEs with small data transmissions. The long connected may cause the control channel very inefficient due to the very long packet inter-arrival time.
Third, for fast moving UEs, the HO signaling would increase and even exceed the signaling of RRC connection establishment.
Although the above problems may be solved by adjusting the DRX parameter, adjusting the inactivity time, and evaluating the “mobility state” specific to each UE, and other manners, all of the above methods need appropriate configurations; otherwise, many UEs in the connection state will waste network resources, waste handover-related signaling, and UE power.